1. Field of the Invention
The present invention relates to a power-switching device and more particularly to a power-switching device with interlock mechanism for an uninterruptible power supply (UPS).
2. Description of the Related Art
To ensure more stable AC power to electric equipment without incurring abnormal operation of the electric equipment as a result of irregular power conditions, such as power failure, power interrupt, under-voltage, surge current and the like, most critical electric appliances are connected to AC power sources through UPSs to constantly supply to the electric appliances for maintaining normal operation of the electric appliances.
As most critical electric appliances must be up and running for a long time or even operated till the end of life cycle as a result of natural wear and damage (for example, military radars), if any foregoing UPS is faulty and needs to be repaired, the AC power source must be directly switched to connect to the electric equipment by a manual bypass means to sustain the operation of the electric appliance. Hence, the UPS to be repaired can then be removed for repairing. The manual bypass means is normally performed through a knob being mechanically actuated to disconnect the AC power source and the UPS and connect the AC power source to the electric equipment instead.
However, if the AC power source is directly switched to connect to the electric equipment by the manual bypass means, the UPS to be repaired may immediately supply power through its output circuit to the electric equipment connected to the AC power source using its backup AC power stored in its energy storage circuit just because the input circuit of the UPS does not detect the AC power source. The outcome may be a reverse current of the AC power source, possibly burning out the input circuit of the UPS.
To tackle that problem, many UPSs have a built-in bypass mode capable of being activated through a trigger switch. When the bypass mode is activated, the UPSs will not output their stored backup AC power when detecting no AC power input and the damage to the input circuits of the UPSs can be avoided accordingly.
Nevertheless, less experienced service personnel may forget to activate the bypass mode through the trigger switch before manually bypassing the UPS and the above-mentioned damage to the UPS still inevitably happens.